1. Field of the Invention
The present invention relates to a system for managing copyrights for displaying, storing, copying, editing, or transferring digital data.
2. Background Art
In the information-oriented society of today, besides normal terrestrial broadcasting, satellite broadcasting, which is referred to as broadcasting satellites (BS) and communication satellites (CS), and cable TV broadcasting, which is referred to as CATV (cable television), using coaxial cables or optical cables are gaining wide spread acceptance.
In a satellite broadcasting or CATV broadcasting which distributes several tens of channels at the same time, scrambled channels of movies, sport events, and music which cannot be viewed through a comprehensive contract are provided in addition to unscrambled general channels. In order to view these scrambled channels, it is necessary to subscribe to descramble the channels; however, a normal subscription period is about one month, and it is often impossible to view through temporary contracts of shorter duration.
In the Japanese Patent Application Laid-Open No. 6-46419 and the Japanese Patent Application Laid-open No. 6-141004, M. Saito proposed a system in which users obtain a viewing permit key from a charging center via a communication line and are charged, and descramble programs scrambled each by a different scramble pattern, using the viewing permit key to view the programs. An apparatus for such a system was also proposed in the Japanese Patent Application Laid-open No. 6-132916.
In these system and apparatus, those who desire to use scrambled programs send a request for viewing to the charging center via a communication line by using a communication apparatus. The charging center transmits the viewing permit key to the communication apparatus corresponding to the request for viewing, and charges and collects the fee.
Users, on receiving the viewing permit key with the communication apparatus, transmit the viewing permit key to a receiving apparatus via direct means connecting the communication apparatus and the receiving apparatus or via indirect means such as flexible disks or the like. The receiving apparatus to which the viewing permit key is transmitted descrambles the programs using the viewing permit key.
Japanese Patent Application Laid-Open No. 6-132916 describes a system and an apparatus for selling and renting a tape or a disk on which a plurality of data scrambled with different scramble patterns respectively are recorded. Specific data can be utilized using the viewing permit key provided by IC cards or the like.
In addition, in today's information-oriented society, computer communication networks are available for mutually using data which are stored independently by each computer. Such computer communication networks include LAN (local area network), WAN (wide area network), or an international network known as Internet.
Recently, a new digitization technique has been developed for reducing the information amount by compressing a television moving picture signal which could not be digitized in the past because of a huge amount of information generated by digitization. So far, H.261 standards for video conference, JPEG (joint photographic image coding experts group) standards for static pictures, MPEG 1 (moving picture image coding experts group 1) standards for storing pictures and MPEG 2 standards to cover the current television broadcast and high-definition television broadcast are available.
The digitization technique using the picture compression technology can be used not only for the television broadcasting or the video picture recording, but also for television moving picture data which could not be handled by computer before. Thus, the "multimedia system" which can handle various types of data used by computers and digitized television moving picture data at the same time has attracted interest as a future technology. This multimedia system is also incorporated in the data communication and can be used as data on the database.
With the utilization range of databases being expanded, the method for charging for the data use on the database, and how to manage copyright problems associated with copying, transmitting other than direct use of data, and also the secondary exploitation right associated with data editing have become important issues. To prevent unauthorized use of data, it is necessary to take measures so that the data cannot be used by users other than authorized users, and data encryption is the best means for this purpose.
For the television systems, database systems or electronic commercial transaction systems or the like, a crypt key is required for encryption and decryption of data. A crypt key must be delivered to data users. However, the whole procedure for encryption and decryption is complicated because of tight security and high reliability requirements.
A general description of cryptography is provided below.
In the cryptography, the encryption to encrypt a plaintext M using a crypt key K and to obtain a cryptogram C is expressed as: EQU C=E(K, M)
and decryption to obtain a plaintext M from the cryptogram C using a crypt key K is expressed as: EQU M=D(K, C).
Further, M. Saito has proposed a concrete arrangement of a data copyright management system in Japanese Patent Application No. JP-A 6-64889. In this system, in order to manage copyrights in display (including the process to turn to audio signal), storage, copying, editing and transferring of digital data in a database system including real-time transmission of digital picture, one or more of the programs to manage the copyrights, copyright information or the copyright management message are transmitted, when needed, in addition to a permit key to allow the user to utilize the encrypted data.
When the user attempts to utilize the data beyond the conditions of the permission or request, a copyright management message is displayed on the screen, to caution or warn the user. The copyright management program watches and manages in such manner that no utilization of data is performed beyond the conditions of request or permission.
The data is encrypted and supplied, and is then decrypted using a permit key to be utilized. When the data is stored in a device, is copied to a medium other than the device, or is transferred outside the device, re-encryption is performed. Also, a permit key is provided for each utilization such as displaying, using, storing, copying, editing, transferring, etc.